The government’s flagship immigration policy, known as the Rwanda plan, is hanging in the balance this morning after the highest court in the land found it to be unlawful.

But what is the scheme? Why is it so controversial? And how has it ended up in the judicial system?

The Rwanda plan was first proposed by Boris Johnson back in April 2022 as the government came under increasing pressure to tackle the growing number of small boats crossing the Channel.

The then prime minister outlined his policy that would see anyone arriving in the country illegally deported to the east African nation.

Those who successfully applied for refugee status when there would then be given the right to remain in Rwanda – not return to the UK.

But if their claim was unsuccessful, they could then be removed to their country of origin.

The deal, signed by the home secretary at the time, Priti Patel, and her Rwandan counterpart, cost the government £120m.

Mr Johnson said it would help deter people from making the dangerous crossing to the UK and tackle the “barbaric trade in human misery” caused by people traffickers.

Opposition parties and charities deemed the plan “cruel and nasty”, and claimed the policy would break international human rights laws.

There were even reports that the King – then the Prince of Wales – was a critic of the scheme.

But the government pushed ahead, with the first flight to Kigali set to take off in June 2022.

Come the day, there were only seven asylum seekers on board the plane.

Numerous court cases were launched by refugee charities, as well as the Public and Commercial Services union, ahead of take-off, calling the policy “inhumane” and demanding the deportations were stopped.

Protesters also tried to stop the flight, locking themselves together with metal pipes and blockading exits of the Colnbrook Immigration Removal Centre at Heathrow, where the migrants were believed to be held.

However, judges in the UK ruled the seven people could be deported, saying there had been an “assurance” from the government that if the policy was found to be unlawful at a later stage, steps would be taken to bring back any migrants.

This didn’t stop further last-minute legal challenges to prevent take-off though.

In the end, the European Court of Human Rights (ECHR) issued injunctions to halt the deportations altogether, leaving the plane grounded on a Ministry of Defence runway.

The government said it would appeal against the ruling, with Tory MPs angered that a European court could overrule the decision of English judges.

But campaigners said it showed the “inhumanity” of the plan for the human rights watchdog to intervene.

In the months that followed, there was a change in government, with Liz Truss taking the keys to Number 10 and Suella Braverman heading up the Home Office.

Both women stood by the Rwanda plan and, even when Ms Truss was ousted weeks later, her successor Rishi Sunak also gave it his backing.

The ruling of the EHRC – which ensures the European Human Rights Convention is adhered to – was still fresh in the minds of Tory backbenchers, as they saw it as holding up the policy they believed would stop the boats.

And it led to a number of calls for the UK to leave the convention, though they appeared to remain in the minority.

The plan itself headed back to the courts as campaigners tried a new tactic to stop it in its tracks, launching a judicial review on the Home Office’s assessment of Rwanda as a safe third country.

The government doubled down on its belief in the scheme – with Ms Braverman telling the Conservative Party conference it was her “dream” to see flights take off.

And come December of 2022, that dream looked closer to reality, as the High Court ruled in the favour of ministers, saying the scheme did not breach either the UN’s Refugee Convention or human rights laws, and that Rwanda was a “safe third country” for migrants to be sent to.

But the legal battle was far from over.

Campaigners were then allowed to appeal the ruling in the Court of Appeal, and the three sitting judges overturned the High Court’s decision.

Lord Chief Justice Lord Burnett concluded Rwanda was not a safe place for people to be housed while their asylum claims were processed, adding: “The result is that the High Court’s decision that Rwanda was a safe third country is reversed, and unless and until the deficiencies in its asylum process are corrected, removal of asylum seekers will be unlawful.”

The government was outraged, with the prime minister saying he “fundamentally disagreed” with the ruling, and would do “whatever is necessary” to get the removal flights going.

The anger of Ms Braverman and her right-wing supporters also grew, with further demands to leave the ECHR, and others calling for the human rights convention to be overhauled.

The government got approval to appeal that ruling and, as a result, it was sent to the Supreme Court.

The judgment delivered by the Supreme Court President Lord Rees found that the Court of Appeal had been right to overturn the original decision of the High Court.

He said the justices had unanimously concluded those sent to the country would be at “real risk” of being returned home, whether their grounds to claim asylum were justified or not.

The full judgment said those sent to Rwanda would be at risk of re-foulement – where a refugee is returned to their country of origin where there is a substantial risk they could be subjected to torture.

The court ruling said the principle of re-foulement is not just a breach of the European Human Rights Convention, but a number of other international treaties.

Mr Sunak said ministers would now “consider next steps”.